The number of microporous crystalline compositions number well in the hundreds. These range from zeolites which are crystalline aluminosilicate compositions to metal sulfide molecular sieves (see U.S. Pat. No. 4,880,761). In general, the crystalline zeolites are formed from corner-sharing AlO.sub.2 and SiO.sub.2 tetrahedra and are characterized by having pore openings of uniform dimensions, having a significant ion-exchange capacity, and being capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal, without significantly displacing any atoms which make up the permanent crystal structure.
Non-zeolite molecular sieves are those which do not contain both AlO.sub.2 and SiO.sub.2 tetrahedra as essential framework constituents, but which exhibit the ion-exchange and/or adsorption characteristics of the zeolites. These include: 1) crystalline aluminophosphate compositions disclosed in U.S. Pat. No. 4,310,440; 2) silicon substituted aluminophosphates as disclosed in U.S. Pat. No. 4,440,871; 3) metal substituted aluminophosphates as disclosed in U.S. Pat. No. 4,853,197; and 4) metallo zinc-phosphate compositions disclosed in U.S. Pat. No. 5,302,362.
Applicants have now synthesized a new family of crystalline microporous compositions which have indium and silicon as the framework elements. These compositions can be described by the empirical formula: EQU A.sub.p (In.sub.1-n M.sub.n).sub.y Si.sub.1-z Ge.sub.z O.sub.x
where A is a cation selected from the group consisting of alkali metals, alkaline earth metal, ammonium ion, hydronium ion and mixtures thereof, "p" is the mole fraction of A and varies from about 0.5y to about 3y, M is an element having a valence of +3, +4 or +5, "n" is the mole fraction of M and varies from 0 to about 0.9, "x" has a value from about 2+y to about 2+5y, "y" has a value of about 0.25 to about 1 and "z" has a value from 0 to about 0.9.
Although indium silicates are known in the art, to applicants' knowledge there is no disclosure of crystalline and microporous indium silicates as described above. For example, T. Gaewdang et al. in Z. Anorg. Allg. Chem. 620 (1994) 1965-1970 describe indium silicates and indium germanates with crystal structures similar to thortveitite which is a dense phase composition. A. N. Christensen and R. G. Hazell in Acta Chemica Scandinavica 21 (1967) 1425-1429 disclose that a composition with the formula NaIn(SiO.sub.3).sub.2 has the diopside structure, also a dense phase. Bukeikhanovie et al. in Catalysis Letters 50 (1998) 93-105 disclose an amorphous indium silicate which is microporous. Finally, Chatterjee et al. in Microporous and Mesoporous Materials, 20 (1998) 87-91 disclose the synthesis of a zeolite beta containing indium. The ratio of SiO.sub.2 /In.sub.2 O.sub.3 is 40 or higher. In contrast, applicants' compositions have a Si/In ratio from 4:1 to 1:1 in non M-containing compositions. Further, applicants' compositions differ from the other references in that they are both crystalline and microporous.